Organic Electroluminescent Materials and Devices

ABSTRACT

Metal complexes containing heteroaryl and its analogues as ligands are disclosed in this application. These compounds may be useful as charge transport materials in OLEDs.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application Ser. No. 62/436,044, filed Dec. 19, 2016, the entire contents of which is incorporated herein by reference.

FIELD

The present invention relates to compounds for use as hosts and devices, such as organic light emitting diodes, including the same.

BACKGROUND

Opto-electronic devices that make use of organic materials are becoming increasingly desirable for a number of reasons. Many of the materials used to make such devices are relatively inexpensive, so organic opto-electronic devices have the potential for cost advantages over inorganic devices. In addition, the inherent properties of organic materials, such as their flexibility, may make them well suited for particular applications such as fabrication on a flexible substrate. Examples of organic opto-electronic devices include organic light emitting diodes/devices (OLEDs), organic phototransistors, organic photovoltaic cells, and organic photodetectors. For OLEDs, the organic materials may have performance advantages over conventional materials. For example, the wavelength at which an organic emissive layer emits light may generally be readily tuned with appropriate dopants.

OLEDs make use of thin organic films that emit light when voltage is applied across the device. OLEDs are becoming an increasingly interesting technology for use in applications such as flat panel displays, illumination, and backlighting. Several OLED materials and configurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and 5,707,745, which are incorporated herein by reference in their entirety.

One application for phosphorescent emissive molecules is a full color display. Industry standards for such a display call for pixels adapted to emit particular colors, referred to as “saturated” colors. In particular, these standards call for saturated red, green, and blue pixels. Alternatively the OLED can be designed to emit white light. In conventional liquid crystal displays emission from a white backlight is filtered using absorption filters to produce red, green and blue emission. The same technique can also be used with OLEDs. The white OLED can be either a single EML device or a stack structure. Color may be measured using CIE coordinates, which are well known to the art.

One example of a green emissive molecule is tris(2-phenylpyridine) iridium, denoted Ir(ppy)₃, which has the following structure:

In this, and later figures herein, we depict the dative bond from nitrogen to metal (here, Ir) as a straight line.

As used herein, the term “organic” includes polymeric materials as well as small molecule organic materials that may be used to fabricate organic opto-electronic devices. “Small molecule” refers to any organic material that is not a polymer, and “small molecules” may actually be quite large. Small molecules may include repeat units in some circumstances. For example, using a long chain alkyl group as a substituent does not remove a molecule from the “small molecule” class. Small molecules may also be incorporated into polymers, for example as a pendent group on a polymer backbone or as a part of the backbone. Small molecules may also serve as the core moiety of a dendrimer, which consists of a series of chemical shells built on the core moiety. The core moiety of a dendrimer may be a fluorescent or phosphorescent small molecule emitter. A dendrimer may be a “small molecule,” and it is believed that all dendrimers currently used in the field of OLEDs are small molecules.

As used herein, “top” means furthest away from the substrate, while “bottom” means closest to the substrate. Where a first layer is described as “disposed over” a second layer, the first layer is disposed further away from substrate. There may be other layers between the first and second layer, unless it is specified that the first layer is “in contact with” the second layer. For example, a cathode may be described as “disposed over” an anode, even though there are various organic layers in between.

As used herein, “solution processible” means capable of being dissolved, dispersed, or transported in and/or deposited from a liquid medium, either in solution or suspension form.

A ligand may be referred to as “photoactive” when it is believed that the ligand directly contributes to the photoactive properties of an emissive material. A ligand may be referred to as “ancillary” when it is believed that the ligand does not contribute to the photoactive properties of an emissive material, although an ancillary ligand may alter the properties of a photoactive ligand.

As used herein, and as would be generally understood by one skilled in the art, a first “Highest Occupied Molecular Orbital” (HOMO) or “Lowest Unoccupied Molecular Orbital” (LUMO) energy level is “greater than” or “higher than” a second HOMO or LUMO energy level if the first energy level is closer to the vacuum energy level. Since ionization potentials (IP) are measured as a negative energy relative to a vacuum level, a higher HOMO energy level corresponds to an IP having a smaller absolute value (an IP that is less negative). Similarly, a higher LUMO energy level corresponds to an electron affinity (EA) having a smaller absolute value (an EA that is less negative). On a conventional energy level diagram, with the vacuum level at the top, the LUMO energy level of a material is higher than the HOMO energy level of the same material. A “higher” HOMO or LUMO energy level appears closer to the top of such a diagram than a “lower” HOMO or LUMO energy level.

As used herein, and as would be generally understood by one skilled in the art, a first work function is “greater than” or “higher than” a second work function if the first work function has a higher absolute value. Because work functions are generally measured as negative numbers relative to vacuum level, this means that a “higher” work function is more negative. On a conventional energy level diagram, with the vacuum level at the top, a “higher” work function is illustrated as further away from the vacuum level in the downward direction. Thus, the definitions of HOMO and LUMO energy levels follow a different convention than work functions.

More details on OLEDs, and the definitions described above, can be found in U.S. Pat. No. 7,279,704, which is incorporated herein by reference in its entirety.

There is a need in the art for novel metal complexes useful as charge transport materials in OLEDs. The present invention satisfies this need in the art.

SUMMARY

According to an embodiment, a compound is provided comprising a ligand L_(A) having the formula:

wherein X¹ is selected from the group consisting of O, S, Se, NR, CRR′, SiRR′, and

wherein L_(A) is coordinated to a metal M selected from the group consisting of Li, Be, Mg, Al, Ga, and Zn;

wherein L_(A) is optionally linked with other ligands to comprise a tridentate to possible maximum dentate ligand;

wherein M is optionally coordinated to other ligands;

wherein when X¹ is selected from the group consisting of O, S, and Se; then M is Li;

wherein when X¹ is selected from the group consisting of NR, CRR′, SiRR′; then at least one pair of adjacent Z¹ to Z³, or Z⁴ to Z⁶ are carbon atoms of which R¹ or R² attached thereto form a di-substitution having the following formula and are fused to ring A or B;

wherein the wave lines indicate bonds to ring A or B;

wherein X² is selected from the group consisting of O, S, Se, NR, CRR′, and SiRR′;

wherein Z¹ to Z¹⁴ are each independently selected from the group consisting of carbon and nitrogen;

wherein R¹ to R⁴ each independently represent a mono to possible maximum number of substitution, or no substitution;

wherein R¹ to R⁴, R, and R′ are each independently selected from the group consisting of hydrogen, deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; and wherein any two adjacent substituents are optionally joined to form a ring.

According to another embodiment, a device comprising one or more organic light emitting devices is also provided. At least one of the one or more organic light emitting devices can include an anode, a cathode, and an organic layer, disposed between the anode and the cathode, wherein the organic layer can include a compound comprising a ligand L_(A). The device can be a consumer product, an electronic component module, an organic light-emitting device, and/or a lighting panel.

According to yet another embodiment, a formulation comprising a compound comprising a ligand L_(A) is provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an organic light emitting device.

FIG. 2 shows an inverted organic light emitting device that does not have a separate electron transport layer.

DETAILED DESCRIPTION

Generally, an OLED comprises at least one organic layer disposed between and electrically connected to an anode and a cathode. When a current is applied, the anode injects holes and the cathode injects electrons into the organic layer(s). The injected holes and electrons each migrate toward the oppositely charged electrode. When an electron and hole localize on the same molecule, an “exciton,” which is a localized electron-hole pair having an excited energy state, is formed. Light is emitted when the exciton relaxes via a photoemissive mechanism. In some cases, the exciton may be localized on an excimer or an exciplex. Non-radiative mechanisms, such as thermal relaxation, may also occur, but are generally considered undesirable.

The initial OLEDs used emissive molecules that emitted light from their singlet states (“fluorescence”) as disclosed, for example, in U.S. Pat. No. 4,769,292, which is incorporated by reference in its entirety. Fluorescent emission generally occurs in a time frame of less than 10 nanoseconds.

More recently, OLEDs having emissive materials that emit light from triplet states (“phosphorescence”) have been demonstrated. Baldo et al., “Highly Efficient Phosphorescent Emission from Organic Electroluminescent Devices,” Nature, vol. 395, 151-154, 1998; (“Baldo-I”) and Baldo et al., “Very high-efficiency green organic light-emitting devices based on electrophosphorescence,” Appl. Phys. Lett., vol. 75, No. 3, 4-6 (1999) (“Baldo-II”), are incorporated by reference in their entireties. Phosphorescence is described in more detail in U.S. Pat. No. 7,279,704 at cols. 5-6, which are incorporated by reference.

FIG. 1 shows an organic light emitting device 100. The figures are not necessarily drawn to scale. Device 100 may include a substrate 110, an anode 115, a hole injection layer 120, a hole transport layer 125, an electron blocking layer 130, an emissive layer 135, a hole blocking layer 140, an electron transport layer 145, an electron injection layer 150, a protective layer 155, a cathode 160, and a barrier layer 170. Cathode 160 is a compound cathode having a first conductive layer 162 and a second conductive layer 164. Device 100 may be fabricated by depositing the layers described, in order. The properties and functions of these various layers, as well as example materials, are described in more detail in U.S. Pat. No. 7,279,704 at cols. 6-10, which are incorporated by reference.

More examples for each of these layers are available. For example, a flexible and transparent substrate-anode combination is disclosed in U.S. Pat. No. 5,844,363, which is incorporated by reference in its entirety. An example of a p-doped hole transport layer is m-MTDATA doped with F₄-TCNQ at a molar ratio of 50:1, as disclosed in U.S. Patent Application Publication No. 2003/0230980, which is incorporated by reference in its entirety. Examples of emissive and host materials are disclosed in U.S. Pat. No. 6,303,238 to Thompson et al., which is incorporated by reference in its entirety. An example of an n-doped electron transport layer is BPhen doped with Li at a molar ratio of 1:1, as disclosed in U.S. Patent Application Publication No. 2003/0230980, which is incorporated by reference in its entirety. U.S. Pat. Nos. 5,703,436 and 5,707,745, which are incorporated by reference in their entireties, disclose examples of cathodes including compound cathodes having a thin layer of metal such as Mg:Ag with an overlying transparent, electrically-conductive, sputter-deposited ITO layer. The theory and use of blocking layers is described in more detail in U.S. Pat. No. 6,097,147 and U.S. Patent Application Publication No. 2003/0230980, which are incorporated by reference in their entireties. Examples of injection layers are provided in U.S. Patent Application Publication No. 2004/0174116, which is incorporated by reference in its entirety. A description of protective layers may be found in U.S. Patent Application Publication No. 2004/0174116, which is incorporated by reference in its entirety.

FIG. 2 shows an inverted OLED 200. The device includes a substrate 210, a cathode 215, an emissive layer 220, a hole transport layer 225, and an anode 230. Device 200 may be fabricated by depositing the layers described, in order. Because the most common OLED configuration has a cathode disposed over the anode, and device 200 has cathode 215 disposed under anode 230, device 200 may be referred to as an “inverted” OLED. Materials similar to those described with respect to device 100 may be used in the corresponding layers of device 200. FIG. 2 provides one example of how some layers may be omitted from the structure of device 100.

The simple layered structure illustrated in FIGS. 1 and 2 is provided by way of non-limiting example, and it is understood that embodiments of the invention may be used in connection with a wide variety of other structures. The specific materials and structures described are exemplary in nature, and other materials and structures may be used. Functional OLEDs may be achieved by combining the various layers described in different ways, or layers may be omitted entirely, based on design, performance, and cost factors. Other layers not specifically described may also be included. Materials other than those specifically described may be used. Although many of the examples provided herein describe various layers as comprising a single material, it is understood that combinations of materials, such as a mixture of host and dopant, or more generally a mixture, may be used. Also, the layers may have various sublayers. The names given to the various layers herein are not intended to be strictly limiting. For example, in device 200, hole transport layer 225 transports holes and injects holes into emissive layer 220, and may be described as a hole transport layer or a hole injection layer. In one embodiment, an OLED may be described as having an “organic layer” disposed between a cathode and an anode. This organic layer may comprise a single layer, or may further comprise multiple layers of different organic materials as described, for example, with respect to FIGS. 1 and 2.

Structures and materials not specifically described may also be used, such as OLEDs comprised of polymeric materials (PLEDs) such as disclosed in U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated by reference in its entirety. By way of further example, OLEDs having a single organic layer may be used. OLEDs may be stacked, for example as described in U.S. Pat. No. 5,707,745 to Forrest et al, which is incorporated by reference in its entirety. The OLED structure may deviate from the simple layered structure illustrated in FIGS. 1 and 2. For example, the substrate may include an angled reflective surface to improve out-coupling, such as a mesa structure as described in U.S. Pat. No. 6,091,195 to Forrest et al., and/or a pit structure as described in U.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated by reference in their entireties.

Unless otherwise specified, any of the layers of the various embodiments may be deposited by any suitable method. For the organic layers, preferred methods include thermal evaporation, ink-jet, such as described in U.S. Pat. Nos. 6,013,982 and 6,087,196, which are incorporated by reference in their entireties, organic vapor phase deposition (OVPD), such as described in U.S. Pat. No. 6,337,102 to Forrest et al., which is incorporated by reference in its entirety, and deposition by organic vapor jet printing (OVJP), such as described in U.S. Pat. No. 7,431,968, which is incorporated by reference in its entirety. Other suitable deposition methods include spin coating and other solution based processes. Solution based processes are preferably carried out in nitrogen or an inert atmosphere. For the other layers, preferred methods include thermal evaporation. Preferred patterning methods include deposition through a mask, cold welding such as described in U.S. Pat. Nos. 6,294,398 and 6,468,819, which are incorporated by reference in their entireties, and patterning associated with some of the deposition methods such as ink-jet and OVJD. Other methods may also be used. The materials to be deposited may be modified to make them compatible with a particular deposition method. For example, substituents such as alkyl and aryl groups, branched or unbranched, and preferably containing at least 3 carbons, may be used in small molecules to enhance their ability to undergo solution processing. Substituents having 20 carbons or more may be used, and 3-20 carbons is a preferred range. Materials with asymmetric structures may have better solution processibility than those having symmetric structures, because asymmetric materials may have a lower tendency to recrystallize. Dendrimer substituents may be used to enhance the ability of small molecules to undergo solution processing.

Devices fabricated in accordance with embodiments of the present invention may further optionally comprise a barrier layer. One purpose of the barrier layer is to protect the electrodes and organic layers from damaging exposure to harmful species in the environment including moisture, vapor and/or gases, etc. The barrier layer may be deposited over, under or next to a substrate, an electrode, or over any other parts of a device including an edge. The barrier layer may comprise a single layer, or multiple layers. The barrier layer may be formed by various known chemical vapor deposition techniques and may include compositions having a single phase as well as compositions having multiple phases. Any suitable material or combination of materials may be used for the barrier layer. The barrier layer may incorporate an inorganic or an organic compound or both. The preferred barrier layer comprises a mixture of a polymeric material and a non-polymeric material as described in U.S. Pat. No. 7,968,146, PCT Pat. Application Nos. PCT/US2007/023098 and PCT/US2009/042829, which are herein incorporated by reference in their entireties. To be considered a “mixture”, the aforesaid polymeric and non-polymeric materials comprising the barrier layer should be deposited under the same reaction conditions and/or at the same time. The weight ratio of polymeric to non-polymeric material may be in the range of 95:5 to 5:95. The polymeric material and the non-polymeric material may be created from the same precursor material. In one example, the mixture of a polymeric material and a non-polymeric material consists essentially of polymeric silicon and inorganic silicon.

Devices fabricated in accordance with embodiments of the invention can be incorporated into a wide variety of electronic component modules (or units) that can be incorporated into a variety of electronic products or intermediate components. Examples of such electronic products or intermediate components include display screens, lighting devices such as discrete light source devices or lighting panels, etc. that can be utilized by the end-user product manufacturers. Such electronic component modules can optionally include the driving electronics and/or power source(s). Devices fabricated in accordance with embodiments of the invention can be incorporated into a wide variety of consumer products that have one or more of the electronic component modules (or units) incorporated therein. Such consumer products would include any kind of products that include one or more light source(s) and/or one or more of some type of visual displays. Some examples of such consumer products include flat panel displays, computer monitors, medical monitors, televisions, billboards, lights for interior or exterior illumination and/or signaling, heads-up displays, fully or partially transparent displays, flexible displays, laser printers, telephones, cell phones, tablets, phablets, personal digital assistants (PDAs), wearable device, laptop computers, digital cameras, camcorders, viewfinders, micro-displays, 3-D displays, virtual reality or augmented reality displays, vehicles, a large area wall, theater or stadium screen, or a sign. Various control mechanisms may be used to control devices fabricated in accordance with the present invention, including passive matrix and active matrix. Many of the devices are intended for use in a temperature range comfortable to humans, such as 18 degrees C. to 30 degrees C., and more preferably at room temperature (20-25 degrees C.), but could be used outside this temperature range, for example, from −40 degree C. to +80 degree C.

The materials and structures described herein may have applications in devices other than OLEDs. For example, other optoelectronic devices such as organic solar cells and organic photodetectors may employ the materials and structures. More generally, organic devices, such as organic transistors, may employ the materials and structures.

The term “halo,” “halogen,” or “halide” as used herein includes fluorine, chlorine, bromine, and iodine.

The term “alkyl” as used herein contemplates both straight and branched chain alkyl radicals. Preferred alkyl groups are those containing from one to fifteen carbon atoms and includes methyl, ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl, 2-methylpropyl, pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl, and the like. Additionally, the alkyl group may be optionally substituted.

The term “cycloalkyl” as used herein contemplates cyclic alkyl radicals. Preferred cycloalkyl groups are those containing 3 to 10 ring carbon atoms and includes cyclopropyl, cyclopentyl, cyclohexyl, adamantyl, and the like. Additionally, the cycloalkyl group may be optionally substituted.

The term “alkenyl” as used herein contemplates both straight and branched chain alkene radicals. Preferred alkenyl groups are those containing two to fifteen carbon atoms. Additionally, the alkenyl group may be optionally substituted.

The term “alkynyl” as used herein contemplates both straight and branched chain alkyne radicals. Preferred alkynyl groups are those containing two to fifteen carbon atoms. Additionally, the alkynyl group may be optionally substituted.

The terms “aralkyl” or “arylalkyl” as used herein are used interchangeably and contemplate an alkyl group that has as a substituent an aromatic group. Additionally, the aralkyl group may be optionally substituted.

The term “heterocyclic group” as used herein contemplates aromatic and non-aromatic cyclic radicals. Hetero-aromatic cyclic radicals also means heteroaryl. Preferred hetero-non-aromatic cyclic groups are those containing 3 to 7 ring atoms which includes at least one hetero atom, and includes cyclic amines such as morpholino, piperdino, pyrrolidino, and the like, and cyclic ethers, such as tetrahydrofuran, tetrahydropyran, and the like. Additionally, the heterocyclic group may be optionally substituted.

The term “aryl” or “aromatic group” as used herein contemplates single-ring groups and polycyclic ring systems. The polycyclic rings may have two or more rings in which two carbons are common to two adjoining rings (the rings are “fused”) wherein at least one of the rings is aromatic, e.g., the other rings can be cycloalkyls, cycloalkenyls, aryl, heterocycles, and/or heteroaryls. Preferred aryl groups are those containing six to thirty carbon atoms, preferably six to twenty carbon atoms, more preferably six to twelve carbon atoms. Especially preferred is an aryl group having six carbons, ten carbons or twelve carbons. Suitable aryl groups include phenyl, biphenyl, triphenyl, triphenylene, tetraphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, and azulene, preferably phenyl, biphenyl, triphenyl, triphenylene, fluorene, and naphthalene. Additionally, the aryl group may be optionally substituted.

The term “heteroaryl” as used herein contemplates single-ring hetero-aromatic groups that may include from one to five heteroatoms. The term heteroaryl also includes polycyclic hetero-aromatic systems having two or more rings in which two atoms are common to two adjoining rings (the rings are “fused”) wherein at least one of the rings is a heteroaryl, e.g., the other rings can be cycloalkyls, cycloalkenyls, aryl, heterocycles, and/or heteroaryls. Preferred heteroaryl groups are those containing three to thirty carbon atoms, preferably three to twenty carbon atoms, more preferably three to twelve carbon atoms. Suitable heteroaryl groups include dibenzothiophene, dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran, benzothiophene, benzoselenophene, carbazole, indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole, oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine, benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine, benzofuropyridine, furodipyridine, benzothienopyridine, thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine, preferably dibenzothiophene, dibenzofuran, dibenzoselenophene, carbazole, indolocarbazole, imidazole, pyridine, triazine, benzimidazole, 1,2-azaborine, 1,3-azaborine, 1,4-azaborine, borazine, and aza-analogs thereof. Additionally, the heteroaryl group may be optionally substituted.

The alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, heterocyclic group, aryl, and heteroaryl may be unsubstituted or may be substituted with one or more substituents selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, cyclic amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof.

As used herein, “substituted” indicates that a substituent other than H is bonded to the relevant position, such as carbon. Thus, for example, where R¹ is mono-substituted, then one R¹ must be other than H. Similarly, where R¹ is di-substituted, then two of R¹ must be other than H. Similarly, where R¹ is unsubstituted, R¹ is hydrogen for all available positions.

The “aza” designation in the fragments described herein, i.e. aza-dibenzofuran, aza-dibenzothiophene, etc. means that one or more of the C—H groups in the respective fragment can be replaced by a nitrogen atom, for example, and without any limitation, azatriphenylene encompasses both dibenzo[f,h]quinoxaline and dibenzo[f,h]quinoline. One of ordinary skill in the art can readily envision other nitrogen analogs of the aza-derivatives described above, and all such analogs are intended to be encompassed by the terms as set forth herein.

It is to be understood that when a molecular fragment is described as being a substituent or otherwise attached to another moiety, its name may be written as if it were a fragment (e.g. phenyl, phenylene, naphthyl, dibenzofuryl) or as if it were the whole molecule (e.g. benzene, naphthalene, dibenzofuran). As used herein, these different ways of designating a substituent or attached fragment are considered to be equivalent.

It is hypothesized that the internal quantum efficiency (IQE) of fluorescent OLEDs can exceed the 25% spin statistics limit through delayed fluorescence. As described herein, there are two types of delayed fluorescence, i.e. P-type delayed fluorescence and E-type delayed fluorescence. P-type delayed fluorescence is generated from triplet-triplet annihilation (TTA).

On the other hand, E-type delayed fluorescence does not rely on the collision of two triplets, but rather on the thermal population between the triplet states and the singlet excited states. Compounds that are capable of generating E-type delayed fluorescence are required to have very small singlet-triplet gaps. Thermal energy can activate the transition from the triplet state back to the singlet state. This type of delayed fluorescence is also known as thermally activated delayed fluorescence (TADF). A distinctive feature of TADF is that the delayed component increases as temperature rises due to the increased thermal energy. If the reverse intersystem crossing rate is fast enough to minimize the non-radiative decay from the triplet state, the fraction of back populated singlet excited states can potentially reach 75%. The total singlet fraction can be 100%, far exceeding the spin statistics limit for electrically generated excitons.

E-type delayed fluorescence characteristics can be found in an exciplex system or in a single compound. Without being bound by theory, it is believed that E-type delayed fluorescence requires the luminescent material to have a small singlet-triplet energy gap (ΔE_(S-T)). Organic, non-metal containing, donor-acceptor luminescent materials may be able to achieve this. The emission in these materials is often characterized as a donor-acceptor charge-transfer (CT) type emission. The spatial separation of the HOMO and LUMO in these donor-acceptor type compounds often results in small ΔE_(S-T). These states may involve CT states. Often, donor-acceptor luminescent materials are constructed by connecting an electron donor moiety such as amino- or carbazole-derivatives and an electron acceptor moiety such as N-containing six-membered aromatic ring.

In one aspect, the present invention includes novel metal complexes comprising a heteroaryl and analogues as ligands. These compounds have appropriate charge transport properties and may be useful as charge transport materials in electroluminescent devices.

Compounds of the Invention

In one aspect, the present invention includes a compound comprising a ligand L_(A) having the formula:

wherein X¹ is selected from the group consisting of O, S, Se, NR, CRR′, SiRR′, and

wherein L_(A) is coordinated to a metal M selected from the group consisting of Li, Be, Mg, Al, Ga, and Zn;

wherein L_(A) is optionally linked with other ligands to comprise a tridentate to possible maximum dentate ligand;

wherein M is optionally coordinated to other ligands;

wherein when X¹ is selected from the group consisting of O, S, and Se; then M is Li;

wherein when X¹ is selected from the group consisting of NR, CRR′, SiRR′; then at least one pair of adjacent Z¹ to Z³, or Z⁴ to Z⁶ are carbon atoms of which R¹ or R² attached thereto form a di-substitution having the following formula and are fused to ring A or B;

wherein the wave lines indicate bonds to ring A or B;

wherein X² is selected from the group consisting of O, S, Se, NR, CRR′, and SiRR′;

wherein Z¹ to Z¹⁴ are each independently selected from the group consisting of carbon and nitrogen;

wherein R¹ to R⁴ each independently represent a mono to possible maximum number of substitution, or no substitution;

wherein R¹ to R⁴, R, and R′ are each independently selected from the group consisting of hydrogen, deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; and wherein any two adjacent substituents are optionally joined to form a ring.

In one embodiment, X¹ is selected from the group consisting of O, S, and Se. In another embodiment, X¹ is selected from the group consisting of NR, CRR′, and SiRR′.

In one embodiment, the ligand L_(A) is:

In one embodiment, the ligand L_(A) is selected from the group consisting of:

In one embodiment, Z¹ to Z¹⁴ are each a carbon atom. In another embodiment, at least one of Z¹ to Z¹⁴ is nitrogen atom. In another embodiment, one of Z¹ to Z¹⁴ is nitrogen atom, and the remaining Z¹ to Z¹⁴ are carbon atoms.

In one embodiment, each six-membered ring in the ligand L_(A) has no more than one nitrogen atom.

In one embodiment, the compound is selected from the group consisting of LiL_(A), Be(L_(A))₂, Mg(L_(A))₂, Al(L_(A))₃, Ga(L_(A))₃, and Zn(L_(A))₂. In another embodiment, the compound is heteroleptic.

In one embodiment, the compound is selected from the group consisting of:

  Compound 1, wherein X¹ is O; Compound 2, wherein X¹ is S; Compound 3, wherein X¹ is Se;

  Compound 4, wherein X¹ is O; Compound 5, wherein X¹ is S; Compound 6, wherein X¹ is Se;

  Compound 7, wherein X¹ is O; Compound 8, wherein X¹ is S; Compound 9, wherein X¹ is Se;

  Compound 10, wherein X¹ is O; Compound 11, wherein X¹ is S; Compound 12, wherein X¹ is Se;

  Compound 13, wherein X¹ is O; Compound 14, wherein X¹ is S; Compound 15, wherein X¹ is Se;

  Compound 16, wherein X¹ is O; Compound 17, wherein X¹ is S; Compound 18, wherein X¹ is Se;

  Compound 19, wherein X¹ is O; Compound 20, wherein X¹ is S; Compound 21, wherein X¹ is Se;

  Compound 22, wherein X¹ is O; Compound 23, wherein X¹ is S; Compound 24, wherein X¹ is Se;

  Compound 25, wherein X¹ is O; Compound 26, wherein X¹ is S; Compound 27, wherein X¹ is Se;

  Compound 28, wherein X¹ is O; Compound 29, wherein X¹ is S; Compound 30, wherein X¹ is Se;

Structure ID n M Compound 31 Compound 32 Compound 33 Compound 34 Compound 35

1 2 3 3 2 Li Be Al Ga Zn Compound 36 Compound 37 Compound 38 Compound 39 Compound 40

1 2 3 3 2 Li Be Al Ga Zn Compound 41 Compound 42 Compound 43 Compound 44 Compound 45

1 2 3 3 2 Li Be Al Ga Zn Compound 46 Compound 47 Compound 48 Compound 49 Compound 50

1 2 3 3 2 Li Be Al Ga Zn Compound 51 Compound 52 Compound 53 Compound 54 Compound 55

1 2 3 3 2 Li Be Al Ga Zn Compound 56 Compound 57 Compound 58 Compound 59 Compound 60

1 2 3 3 2 Li Be Al Ga Zn Compound 61 Compound 62 Compound 63 Compound 64 Compound 65

1 2 3 3 2 Li Be Al Ga Zn Compound 66 Compound 67 Compound 68 Compound 69 Compound 70

1 2 3 3 2 Li Be Al Ga Zn Compound 71 Compound 72 Compound 73 Compound 74 Compound 75

1 2 3 3 2 Li Be Al Ga Zn Compound 76 Compound 77 Compound 78 Compound 79 Compound 80

1 2 3 3 2 Li Be Al Ga Zn Compound 81 Compound 82 Compound 83 Compound 84 Compound 85

1 2 3 3 2 Li Be Al Ga Zn Structure ID n M X¹ X² Compound 86 Compound 87 Compound 88 Compound 89 Compound 90 Compound 91 Compound 92 Compound 93 Compound 94 Compound 95 Compound 96 Compound 97 Compound 98 Compound 99 Compound 100 Compound 101

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Li Li Li Li Li Li Li Li Li Li Li Li Li Li Li Li O O O O O O S S S S S Se Se Se Se Se O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 102 1 Li Se CMeMe Compound 103 1 Li Se SiMeMe Compound 104 1 Li NPh O Compound 105 1 Li NPh S Compound 106 1 Li NPh Se Compound 107 1 Li NPh NPh Compound 108 1 Li NPh CMeMe Compound 109 1 Li NPh SiMeMe Compound 110 1 Li CMeMe O Compound 111 1 Li CMeMe S Compound 112 1 Li CMeMe Se Compound 113 1 Li CMeMe NPh Compound 114 1 Li CMeMe CMeMe Compound 115 1 Li CMeMe SiMeMe Compound 116 1 Li SiMeMe O Compound 117 1 Li SiMeMe S Compound 118 1 Li SiMeMe Se Compound 119 1 Li SiMeMe NPh Compound 120 1 Li SiMeMe CMeMe Compound 121 1 Li SiMeMe SiMeMe Compound 122 Compound 123 Compound 124 Compound 125 Compound 126 Compound 127 Compound 128 Compound 129 Compound 130 Compound 131 Compound 132 Compound 133 Compound 134 Compound 135 Compound 136 Compound 137

2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Be Be Be Be Be Be Be Be Be Be Be Be Be Be Be Be NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 138 2 Be SiMeMe CMeMe Compound 139 2 Be SiMeMe SiMeMe Compound 140 Compound 141 Compound 142 Compound 143 Compound 144 Compound 145 Compound 146 Compound 147 Compound 148 Compound 149 Compound 150 Compound 151 Compound 152 Compound 153 Compound 154 Compound 155

3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 Al Al Al Al Al Al Al Al Al Al Al Al Al Al Al Al NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 156 3 Al SiMeMe CMeMe Compound 157 3 Al SiMeMe SiMeMe Compound 158 Compound 159 Compound 160 Compound 161 Compound 162 Compound 163 Compound 164 Compound 165 Compound 166 Compound 167 Compound 168 Compound 169 Compound 170 Compound 171 Compound 172 Compound 173

2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 174 2 Zn SiMeMe CMeMe Compound 175 2 Zn SiMeMe SiMeMe Compound 176 Compound 177 Compound 178 Compound 179 Compound 180 Compound 181 Compound 182 Compound 183 Compound 184 Compound 185 Compound 186 Compound 187 Compound 188 Compound 189 Compound 190 Compound 191

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Li Li Li Li Li Li Li Li Li Li Li Li Li Li Li Li O O O O O O S S S S S S Se Se Se Se O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 192 1 Li Se CMeMe Compound 193 1 Li Se SiMeMe Compound 194 1 Li NPh O Compound 195 1 Li NPh S Compound 196 1 Li NPh Se Compound 197 1 Li NPh NPh Compound 198 1 Li NPh CMeMe Compound 199 1 Li NPh SiMeMe Compound 200 1 Li CMeMe O Compound 201 1 Li CMeMe S Compound 202 1 Li CMeMe Se Compound 203 1 Li CMeMe NPh Compound 204 1 Li CMeMe CMeMe Compound 205 1 Li CMeMe SiMeMe Compound 206 1 Li SiMeMe O Compound 207 1 Li SiMeMe S Compound 208 1 Li SiMeMe Se Compound 209 1 Li SiMeMe NPh Compound 210 1 Li SiMeMe CMeMe Compound 211 1 Li SiMeMe SiMeMe Compound 212 Compound 213 Compound 214 Compound 215 Compound 216 Compound 217 Compound 218 Compound 219 Compound 220 Compound 221 Compound 222 Compound 223 Compound 224 Compound 225 Compound 226 Compound 227

2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Be Be Be Be Be Be Be Be Be Be Be Be Be Be Be Be NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 228 2 Be SiMeMe CMeMe Compound 229 2 Be SiMeMe SiMeMe Compound 230 Compound 231 Compound 232 Compound 233 Compound 234 Compound 235 Compound 236 Compound 237 Compound 238 Compound 239 Compound 240 Compound 241 Compound 242 Compound 243 Compound 244 Compound 245

3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 Al Al Al Al Al Al Al Al Al Al Al Al Al Al Al Al NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 246 3 Al SiMeMe CMeMe Compound 247 3 Al SiMeMe SiMeMe Compound 248 Compound 249 Compound 250 Compound 251 Compound 252 Compound 253 Compound 254 Compound 255 Compound 256 Compound 257 Compound 258 Compound 259 Compound 260 Compound 261 Compound 262 Compound 263

2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 264 2 Zn SiMeMe CMeMe Compound 265 2 Zn SiMeMe SiMeMe Compound 266 Compound 267 Compound 268 Compound 269 Compound 270 Compound 271 Compound 272 Compound 273 Compound 274 Compound 275 Compound 276 Compound 277 Compound 278 Compound 279

1 1 1 1 1 1 1 1 1 1 1 1 1 1 Li Li Li Li Li Li Li Li Li Li Li Li Li Li O O O O O O S S S S S S Se Se O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Compound 280 1 Li Se Se Compound 281 1 Li Se NPh Compound 282 1 Li Se CMeMe Compound 283 1 Li Se SiMeMe Compound 284 1 Li NPh O Compound 285 1 Li NPh S Compound 286 1 Li NPh Se Compound 287 1 Li NPh NPh Compound 288 1 Li NPh CMeMe Compound 289 1 Li NPh SiMeMe Compound 290 1 Li CMeMe O Compound 291 1 Li CMeMe S Compound 292 1 Li CMeMe Se Compound 293 1 Li CMeMe NPh Compound 294 1 Li CMeMe CMeMe Compound 295 1 Li CMeMe SiMeMe Compound 296 1 Li SiMeMe O Compound 297 1 Li SiMeMe S Compound 298 1 Li SiMeMe Se Compound 299 1 Li SiMeMe NPh Compound 300 1 Li SiMeMe CMeMe Compound 301 1 Li SiMeMe SiMeMe Compound 302 Compound 303 Compound 304 Compound 305 Compound 306 Compound 307 Compound 308 Compound 309 Compound 310 Compound 311 Compound 312 Compound 313 Compound 314 Compound 315

2 2 2 2 2 2 2 2 2 2 2 2 2 2 Be Be Be Be Be Be Be Be Be Be Be Be Be Be NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Compound 316 2 Be SiMeMe Se Compound 317 2 Be SiMeMe NPh Compound 318 2 Be SiMeMe CMeMe Compound 319 2 Be SiMeMe SiMeMe Compound 320 Compound 321 Compound 322 Compound 323 Compound 324 Compound 325 Compound 326 Compound 327 Compound 328 Compound 329 Compound 330 Compound 331 Compound 332 Compound 333

3 3 3 3 3 3 3 3 3 3 3 3 3 3 Al Al Al Al Al Al Al Al Al Al Al Al Al Al NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Compound 334 3 Al SiMeMe Se Compound 335 3 Al SiMeMe NPh Compound 336 3 Al SiMeMe CMeMe Compound 337 3 Al SiMeMe SiMeMe Compound 338 Compound 339 Compound 340 Compound 341 Compound 342 Compound 343 Compound 344 Compound 345 Compound 346 Compound 347 Compound 348 Compound 349 Compound 350 Compound 351

2 2 2 2 2 2 2 2 2 2 2 2 2 2 Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Compound 352 2 Zn SiMeMe Se Compound 353 2 Zn SiMeMe NPh Compound 354 2 Zn SiMeMe CMeMe Compound 355 2 Zn SiMeMe SiMeMe Compound 356 Compound 357 Compound 358 Compound 359 Compound 360 Compound 361 Compound 362 Compound 363 Compound 364 Compound 365 Compound 366 Compound 367

1 1 1 1 1 1 1 1 1 1 1 1 Li Li Li Li Li Li Li Li Li Li Li Li O O O O O O S S S S S S O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe Compound 368 1 Li Se O Compound 369 1 Li Se S Compound 370 1 Li Se Se Compound 371 1 Li Se NPh Compound 372 1 Li Se CMeMe Compound 373 1 Li Se SiMeMe Compound 374 1 Li NPh O Compound 375 1 Li NPh S Compound 376 1 Li NPh Se Compound 377 1 Li NPh NPh Compound 378 1 Li NPh CMeMe Compound 379 1 Li NPh SiMeMe Compound 380 1 Li CMeMe O Compound 381 1 Li CMeMe S Compound 382 1 Li CMeMe Se Compound 383 1 Li CMeMe NPh Compound 384 1 Li CMeMe CMeMe Compound 385 1 Li CMeMe SiMeMe Compound 386 1 Li SiMeMe O Compound 387 1 Li SiMeMe S Compound 388 1 Li SiMeMe Se Compound 389 1 Li SiMeMe NPh Compound 390 1 Li SiMeMe CMeMe Compound 391 1 Li SiMeMe SiMeMe Compound 392 Compound 393 Compound 394 Compound 395 Compound 396 Compound 397 Compound 398 Compound 399 Compound 400 Compound 401 Compound 402 Compound 403

2 2 2 2 2 2 2 2 2 2 2 2 Be Be Be Be Be Be Be Be Be Be Be Be NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe Compound 404 2 Be SiMeMe O Compound 405 2 Be SiMeMe S Compound 406 2 Be SiMeMe Se Compound 407 2 Be SiMeMe NPh Compound 408 2 Be SiMeMe CMeMe Compound 409 2 Be SiMeMe SiMeMe Compound 410 Compound 411 Compound 412 Compound 413 Compound 414 Compound 415 Compound 416 Compound 417 Compound 418 Compound 419 Compound 420 Compound 421

3 3 3 3 3 3 3 3 3 3 3 3 Al Al Al Al Al Al Al Al Al Al Al Al NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe Compound 422 3 Al SiMeMe O Compound 423 3 Al SiMeMe S Compound 424 3 Al SiMeMe Se Compound 425 3 Al SiMeMe NPh Compound 426 3 Al SiMeMe CMeMe Compound 427 3 Al SiMeMe SiMeMe Compound 428 Compound 429 Compound 430 Compound 431 Compound 432 Compound 433 Compound 434 Compound 435 Compound 436 Compound 437 Compound 438 Compound 439

2 2 2 2 2 2 2 2 2 2 2 2 Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe Compound 440 2 Zn SiMeMe O Compound 441 2 Zn SiMeMe S Compound 442 2 Zn SiMeMe Se Compound 443 2 Zn SiMeMe NPh Compound 444 2 Zn SiMeMe CMeMe Compound 445 2 Zn SiMeMe SiMeMe Compound 446 Compound 447 Compound 448 Compound 449 Compound 450 Compound 451 Compound 452 Compound 453 Compound 454 Compound 455 Compound 456 Compound 457 Compound 458 Compound 459 Compound 460 Compound 461

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Li Li Li Li Li Li Li Li Li Li Li Li Li Li Li Li O O O O O O S S S S S S Se Se Se Se O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 462 1 Li Se CMeMe Compound 463 1 Li Se SiMeMe Compound 464 1 Li NPh O Compound 465 1 Li NPh S Compound 466 1 Li NPh Se Compound 467 1 Li NPh NPh Compound 468 1 Li NPh CMeMe Compound 469 1 Li NPh SiMeMe Compound 470 1 Li CMeMe O Compound 471 1 Li CMeMe S Compound 472 1 Li CMeMe Se Compound 473 1 Li CMeMe NPh Compound 474 1 Li CMeMe CMeMe Compound 475 1 Li CMeMe SiMeMe Compound 476 1 Li SiMeMe O Compound 477 1 Li SiMeMe S Compound 478 1 Li SiMeMe Se Compound 479 1 Li SiMeMe NPh Compound 480 1 Li SiMeMe CMeMe Compound 481 1 Li SiMeMe SiMeMe Compound 482 Compound 483 Compound 484 Compound 485 Compound 486 Compound 487 Compound 488 Compound 489 Compound 490 Compound 491 Compound 492 Compound 493 Compound 494 Compound 495 Compound 496 Compound 497

2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Be Be Be Be Be Be Be Be Be Be Be Be Be Be Be Be NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 498 2 Be SiMeMe CMeMe Compound 499 2 Be SiMeMe SiMeMe Compound 500 Compound 501 Compound 502 Compound 503 Compound 504 Compound 505 Compound 506 Compound 507 Compound 508 Compound 509 Compound 510 Compound 511 Compound 512 Compound 513 Compound 514 Compound 515

3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 Al Al Al Al Al Al Al Al Al Al Al Al Al Al Al Al NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 516 3 Al SiMeMe CMeMe Compound 517 3 Al SiMeMe SiMeMe Compound 518 Compound 519 Compound 520 Compound 521 Compound 522 Compound 523 Compound 524 Compound 525 Compound 526 Compound 527 Compound 528 Compound 529 Compound 530 Compound 531 Compound 532 Compound 533

2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 534 2 Zn SiMeMe CMeMe Compound 535 2 Zn SiMeMe SiMeMe Compound 536 Compound 537 Compound 538 Compound 539 Compound 540 Compound 541 Compound 542 Compound 543 Compound 544 Compound 545 Compound 546 Compound 547 Compound 548 Compound 549 Compound 550

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Li Li Li Li Li Li Li Li Li Li Li Li Li Li Li O O O O O O S S S S S S Se Se Se O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se Compound 551 1 Li Se NPh Compound 552 1 Li Se CMeMe Compound 553 1 Li Se SiMeMe Compound 554 1 Li NPh O Compound 555 1 Li NPh S Compound 556 1 Li NPh Se Compound 557 1 Li NPh NPh Compound 558 1 Li NPh CMeMe Compound 559 1 Li NPh SiMeMe Compound 560 1 Li CMeMe O Compound 561 1 Li CMeMe S Compound 562 1 Li CMeMe Se Compound 563 1 Li CMeMe NPh Compound 564 1 Li CMeMe CMeMe Compound 565 1 Li CMeMe SiMeMe Compound 566 1 Li SiMeMe O Compound 567 1 Li SiMeMe S Compound 568 1 Li SiMeMe Se Compound 569 1 Li SiMeMe NPh Compound 570 1 Li SiMeMe CMeMe Compound 571 1 Li SiMeMe SiMeMe Compound 572 Compound 573 Compound 574 Compound 575 Compound 576 Compound 577 Compound 578 Compound 579 Compound 580 Compound 581 Compound 582 Compound 583 Compound 584 Compound 585 Compound 586

2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Be Be Be Be Be Be Be Be Be Be Be Be Be Be Be NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se Compound 587 2 Be SiMeMe NPh Compound 588 2 Be SiMeMe CMeMe Compound 589 2 Be SiMeMe SiMeMe Compound 590 Compound 591 Compound 592 Compound 593 Compound 594 Compound 595 Compound 596 Compound 597 Compound 598 Compound 599 Compound 600 Compound 601 Compound 602 Compound 603 Compound 604

3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 Al Al Al Al Al Al Al Al Al Al Al Al Al Al Al NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe SiMeMe Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe Compound 605 3 Al SiMeMe SiMeMe Compound 606 Compound 607 Compound 608 Compound 609 Compound 610 Compound 611 Compound 612 Compound 613 Compound 614 Compound 615 Compound 616 Compound 617 Compound 618 Compound 619 Compound 620

2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se Compound 621 2 Zn SiMeMe NPh Compound 622 2 Zn SiMeMe CMeMe Compound 623 2 Zn SiMeMe SiMeMe Compound 624 Compound 625 Compound 626 Compound 627 Compound 628 Compound 629 Compound 630 Compound 631 Compound 632 Compound 633 Compound 634 Compound 635 Compound 636

1 1 1 1 1 1 1 1 1 1 1 1 1 Li Li Li Li Li Li Li Li Li Li Li Li Li O O O O O O S S S S S S Se O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O Compound 637 1 Li Se S Compound 638 1 Li Se Se Compound 639 1 Li Se NPh Compound 640 1 Li Se CMeMe Compound 641 1 Li Se SiMeMe Compound 642 1 Li NPh O Compound 643 1 Li NPh S Compound 644 1 Li NPh Se Compound 645 1 Li NPh NPh Compound 646 1 Li NPh CMeMe Compound 647 1 Li NPh SiMeMe Compound 648 1 Li CMeMe O Compound 649 1 Li CMeMe S Compound 650 1 Li CMeMe Se Compound 651 1 Li CMeMe NPh Compound 652 1 Li CMeMe CMeMe Compound 653 1 Li SiMeMe O Compound 654 1 Li SiMeMe O Compound 655 1 Li SiMeMe S Compound 656 1 Li SiMeMe Se Compound 657 1 Li SiMeMe NPh Compound 658 1 Li SiMeMe CMeMe Compound 659 1 Li SiMeMe SiMeMe Compound 660 Compound 661 Compound 662 Compound 663 Compound 664 Compound 665 Compound 666 Compound 667 Compound 668 Compound 669 Compound 670 Compound 671 Compound 672

2 2 2 2 2 2 2 2 2 2 2 2 2 Be Be Be Be Be Be Be Be Be Be Be Be Be NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O Compound 673 2 Be SiMeMe S Compound 674 2 Be SiMeMe Se Compound 675 2 Be SiMeMe NPh Compound 676 2 Be SiMeMe CMeMe Compound 677 2 Be SiMeMe SiMeMe Compound 678 Compound 679 Compound 680 Compound 681 Compound 682 Compound 683 Compound 684 Compound 685 Compound 686 Compound 687 Compound 688 Compound 689 Compound 690

3 3 3 3 3 3 3 3 3 3 3 3 3 Al Al Al Al Al Al Al Al Al Al Al Al Al NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O Compound 691 3 Al SiMeMe S Compound 692 3 Al SiMeMe Se Compound 693 3 Al SiMeMe NPh Compound 694 3 Al SiMeMe CMeMe Compound 695 3 Al SiMeMe SiMeMe Compound 696 Compound 697 Compound 698 Compound 699 Compound 700 Compound 701 Compound 702 Compound 703 Compound 704 Compound 705 Compound 706 Compound 707 Compound 708

2 2 2 2 2 2 2 2 2 2 2 2 2 Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O Compound 709 2 Zn SiMeMe S Compound 710 2 Zn SiMeMe Se Compound 711 2 Zn SiMeMe NPh Compound 712 2 Zn SiMeMe CMeMe Compound 713 2 Zn SiMeMe SiMeMe Compound 714 Compound 715 Compound 716 Compound 717 Compound 718 Compound 719 Compound 720 Compound 721 Compound 722 Compound 723 Compound 724 Compound 725 Compound 726 Compound 727 Compound 728 Compound 729

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Li Li Li Li Li Li Li Li Li Li Li Li Li Li Li Li O O O O O O S S S S S S Se Se Se Se O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 730 1 Li Se CMeMe Compound 731 1 Li Se SiMeMe Compound 732 1 Li NPh O Compound 733 1 Li NPh S Compound 734 1 Li NPh Se Compound 735 1 Li NPh NPh Compound 736 1 Li NPh CMeMe Compound 737 1 Li NPh SiMeMe Compound 738 1 Li CMeMe O Compound 739 1 Li CMeMe S Compound 740 1 Li CMeMe Se Compound 741 1 Li CMeMe NPh Compound 742 1 Li CMeMe CMeMe Compound 743 1 Li CMeMe SiMeMe Compound 744 1 Li SiMeMe O Compound 745 1 Li SiMeMe S Compound 746 1 Li SiMeMe Se Compound 747 1 Li SiMeMe NPh Compound 748 1 Li SiMeMe CMeMe Compound 749 1 Li SiMeMe SiMeMe Compound 750 Compound 751 Compound 752 Compound 753 Compound 754 Compound 755 Compound 756 Compound 757 Compound 758 Compound 759 Compound 760 Compound 761 Compound 762 Compound 763 Compound 764 Compound 765

2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Be Be Be Be Be Be Be Be Be Be Be Be Be Be Be Be NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 766 2 Be SiMeMe CMeMe Compound 767 2 Be SiMeMe SiMeMe Compound 768 Compound 769 Compound 770 Compound 771 Compound 772 Compound 773 Compound 774 Compound 775 Compound 776 Compound 777 Compound 778 Compound 779 Compound 780 Compound 781 Compound 782 Compound 783

3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 Al Al Al Al Al Al Al Al Al Al Al Al Al Al Al Al NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 784 3 Al SiMeMe CMeMe Compound 785 3 Al SiMeMe SiMeMe Compound 786 Compound 787 Compound 788 Compound 789 Compound 790 Compound 791 Compound 792 Compound 793 Compound 794 Compound 795 Compound 796 Compound 797 Compound 798 Compound 799 Compound 800 Compound 801

2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 802 2 Zn SiMeMe CMeMe Compound 803 2 Zn SiMeMe SiMeMe

According to another aspect of the present disclosure, an OLED is also provided. The OLED includes an anode, a cathode, and an organic layer disposed between the anode and the cathode. In one embodiment, the OLED includes an anode, a cathode, and a first organic layer disposed between the anode and the cathode. The organic layer may include a host and one or more emitter dopants.

The emitter dopants can be phosphorescent dopants. The organic layer can include a compound comprising a ligand L_(A), and its variations as described herein as a host.

In one embodiment, the organic layer is an emissive layer and the compound comprising a ligand L_(A) is a host. In another embodiment, the organic layer is a blocking layer and the compound comprising a ligand L_(A) is a blocking material in the organic layer. In another embodiment, the organic layer is a transporting layer and the compound comprising a ligand L_(A) is a transporting material in the organic layer. In another embodiment, the first organic layer is an electron injecting layer

In one embodiment, the organic layer further comprises a phosphorescent emissive dopant; wherein the emissive dopant is a transition metal complex having at least one ligand or part of the ligand if the ligand is more than bidentate selected from the group consisting of:

wherein each X¹ to X¹³ are independently selected from the group consisting of carbon and nitrogen;

wherein X is selected from the group consisting of BR′, NR′, PR′, O, S, Se, C═O, S═O, SO₂, CR′R″, SiR′R″, and GeR′R″;

wherein R′ and R″ are optionally fused or joined to form a ring;

wherein each R_(a), R_(b), R_(c), and R_(d) may represent from mono substitution to the possible maximum number of substitution, or no substitution;

wherein R′, R″, R_(a), R_(b), R_(c), and R_(d) are each independently selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; and

wherein any two adjacent substituents of R_(a), R_(b), R_(c), and R_(d) are optionally fused or joined to form a ring or form a multidentate ligand.

In one embodiment, the OLED comprises a second organic layer, wherein the second organic layer is an emitting layer comprising a phosphorescent emissive dopant.

The OLED can be incorporated into one or more of a consumer product, an electronic component module, and a lighting panel.

In yet another aspect of the present disclosure, a formulation comprising a compound comprising a ligand L_(A) is described. The formulation can include one or more components selected from the group consisting of a solvent, a host, a hole injection material, hole transport material, and an electron transport layer material, disclosed herein.

Combination with Other Materials

The materials described herein as useful for a particular layer in an organic light emitting device may be used in combination with a wide variety of other materials present in the device. For example, emissive dopants disclosed herein may be used in conjunction with a wide variety of hosts, transport layers, blocking layers, injection layers, electrodes and other layers that may be present. The materials described or referred to below are non-limiting examples of materials that may be useful in combination with the compounds disclosed herein, and one of skill in the art can readily consult the literature to identify other materials that may be useful in combination.

Conductivity Dopants:

A charge transport layer can be doped with conductivity dopants to substantially alter its density of charge carriers, which will in turn alter its conductivity. The conductivity is increased by generating charge carriers in the matrix material, and depending on the type of dopant, a change in the Fermi level of the semiconductor may also be achieved. Hole-transporting layer can be doped by p-type conductivity dopants and n-type conductivity dopants are used in the electron-transporting layer.

Non-limiting examples of the conductivity dopants that may be used in an OLED in combination with materials disclosed herein are exemplified below together with references that disclose those materials: EP01617493, EP01968131, EP2020694, EP2684932, US20050139810, US20070160905, US20090167167, US2010288362, WO06081780, WO2009003455, WO2009008277, WO2009011327, WO2014009310, US2007252140, US2015060804 and US2012146012.

HIL/HTL:

A hole injecting/transporting material to be used in the present invention is not particularly limited, and any compound may be used as long as the compound is typically used as a hole injecting/transporting material. Examples of the material include, but are not limited to: a phthalocyanine or porphyrin derivative; an aromatic amine derivative; an indolocarbazole derivative; a polymer containing fluorohydrocarbon; a polymer with conductivity dopants; a conducting polymer, such as PEDOT/PSS; a self-assembly monomer derived from compounds such as phosphonic acid and silane derivatives; a metal oxide derivative, such as MoO_(x); a p-type semiconducting organic compound, such as 1,4,5,8,9,12-Hexaazatriphenylenehexacarbonitrile; a metal complex, and a cross-linkable compounds.

Examples of aromatic amine derivatives used in HIL or HTL include, but are not limited to the following general structures:

Each of Ar¹ to Ar⁹ is selected from the group consisting of aromatic hydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, and azulene; the group consisting of aromatic heterocyclic compounds such as dibenzothiophene, dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran, benzothiophene, benzoselenophene, carbazole, indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole, oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine, benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine, benzofuropyridine, furodipyridine, benzothienopyridine, thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine; and the group consisting of 2 to 10 cyclic structural units which are groups of the same type or different types selected from the aromatic hydrocarbon cyclic group and the aromatic heterocyclic group and are bonded to each other directly or via at least one of oxygen atom, nitrogen atom, sulfur atom, silicon atom, phosphorus atom, boron atom, chain structural unit and the aliphatic cyclic group. Each Ar may be unsubstituted or may be substituted by a substituent selected from the group consisting of deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof.

In one aspect, Ar¹ to Ar⁹ is independently selected from the group consisting of:

wherein k is an integer from 1 to 20; X¹⁰¹ to X¹⁰⁸ is C (including CH) or N; Z¹⁰¹ is NAr¹, O, or S; Ar¹ has the same group defined above.

Examples of metal complexes used in HIL or HTL include, but are not limited to the following general formula:

wherein Met is a metal, which can have an atomic weight greater than 40; (Y¹⁰¹-Y¹⁰²) is a bidentate ligand, Y¹⁰¹ and Y¹⁰² are independently selected from C, N, O, P, and S; L¹⁰¹ is an ancillary ligand; k′ is an integer value from 1 to the maximum number of ligands that may be attached to the metal; and k′+k″ is the maximum number of ligands that may be attached to the metal.

In one aspect, (Y¹⁰¹-Y¹⁰²) is a 2-phenylpyridine derivative. In another aspect, (Y¹⁰¹-Y¹⁰²) is a carbene ligand. In another aspect, Met is selected from Ir, Pt, Os, and Zn. In a further aspect, the metal complex has a smallest oxidation potential in solution vs. Fc⁺/Fc couple less than about 0.6 V.

Non-limiting examples of the HIL and HTL materials that may be used in an OLED in combination with materials disclosed herein are exemplified below together with references that disclose those materials: CN102702075, DE102012005215, EP01624500, EP01698613, EP01806334, EP01930964, EP01972613, EP01997799, EP02011790, EP02055700, EP02055701, EP1725079, EP2085382, EP2660300, EP650955, JP07-073529, JP2005112765, JP2007091719, JP2008021687, JP2014-009196, KR20110088898, KR20130077473, TW201139402, U.S. Ser. No. 06/517,957, US20020158242, US20030162053, US20050123751, US20060182993, US20060240279, US20070145888, US20070181874, US20070278938, US20080014464, US20080091025, US20080106190, US20080124572, US20080145707, US20080220265, US20080233434, US20080303417, US2008107919, US20090115320, US20090167161, US2009066235, US2011007385, US20110163302, US2011240968, US2011278551, US2012205642, US2013241401, US20140117329, US2014183517, U.S. Pat. No. 5,061,569, U.S. Pat. No. 5,639,914, WO05075451, WO07125714, WO08023550, WO08023759, WO2009145016, WO2010061824, WO2011075644, WO2012177006, WO2013018530, WO2013039073, WO2013087142, WO2013118812, WO2013120577, WO2013157367, WO2013175747, WO2014002873, WO2014015935, WO2014015937, WO2014030872, WO2014030921, WO2014034791, WO2014104514, WO2014157018.

EBL:

An electron blocking layer (EBL) may be used to reduce the number of electrons and/or excitons that leave the emissive layer. The presence of such a blocking layer in a device may result in substantially higher efficiencies, and or longer lifetime, as compared to a similar device lacking a blocking layer. Also, a blocking layer may be used to confine emission to a desired region of an OLED. In some embodiments, the EBL material has a higher LUMO (closer to the vacuum level) and/or higher triplet energy than the emitter closest to the EBL interface. In some embodiments, the EBL material has a higher LUMO (closer to the vacuum level) and or higher triplet energy than one or more of the hosts closest to the EBL interface. In one aspect, the compound used in EBL contains the same molecule or the same functional groups used as one of the hosts described below.

Additional Hosts:

The light emitting layer of the organic EL device of the present invention preferably contains at least a metal complex as light emitting dopant material, and may contain one or more additional host materials using the metal complex as a dopant material. Examples of the host material are not particularly limited, and any metal complexes or organic compounds may be used as long as the triplet energy of the host is larger than that of the dopant. Any host material may be used with any dopant so long as the triplet criteria is satisfied.

Examples of metal complexes used as host are preferred to have the following general formula:

wherein Met is a metal; (Y¹⁰³-Y¹⁰⁴) is a bidentate ligand, Y¹⁰³ and Y¹⁰⁴ are independently selected from C, N, O, P, and S; L¹⁰¹ is an another ligand; k′ is an integer value from 1 to the maximum number of ligands that may be attached to the metal; and k′+k″ is the maximum number of ligands that may be attached to the metal.

In one aspect, the metal complexes are:

wherein (O—N) is a bidentate ligand, having metal coordinated to atoms O and N.

In another aspect, Met is selected from Ir and Pt. In a further aspect, (Y¹⁰³-Y¹⁰⁴) is a carbene ligand.

Examples of other organic compounds used as additional host are selected from the group consisting of aromatic hydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, azulene; group consisting aromatic heterocyclic compounds such as dibenzothiophene, dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran, benzothiophene, benzoselenophene, carbazole, indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole, oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine, benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine, benzofuropyridine, furodipyridine, benzothienopyridine, thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine; and group consisting 2 to 10 cyclic structural units which are groups of the same type or different types selected from the aromatic hydrocarbon cyclic group and the aromatic heterocyclic group and are bonded to each other directly or via at least one of oxygen atom, nitrogen atom, sulfur atom, silicon atom, phosphorus atom, boron atom, chain structural unit and the aliphatic cyclic group. Wherein each group is further substituted by a substituent selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof.

In one aspect, host compound contains at least one of the following groups in the molecule:

wherein R¹⁰¹ to R¹⁰⁷ is independently selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof, when it is aryl or heteroaryl, it has the similar definition as Ar's mentioned above. k is an integer from 0 to 20 or 1 to 20; k′″ is an integer from 0 to 20. X¹⁰¹ to X¹⁰⁸ is selected from C (including CH) or N. Z¹⁰¹ and Z¹⁰² is selected from NR¹⁰¹, O, or S.

Non-limiting examples of the additional host materials that may be used in an OLED in combination with the host compound disclosed herein are exemplified below together with references that disclose those materials: EP2034538, EP2034538A, EP2757608, JP2007254297, KR20100079458, KR20120088644, KR20120129733, KR20130115564, TW201329200, US20030175553, US20050238919, US20060280965, US20090017330, US20090030202, US20090167162, US20090302743, US20090309488, US20100012931, US20100084966, US20100187984, US2010187984, US2012075273, US2012126221, US2013009543, US2013105787, US2013175519, US2014001446, US20140183503, US20140225088, US2014034914, U.S. Pat. No. 7,154,114, WO2001039234, WO2004093207, WO2005014551, WO2005089025, WO2006072002, WO2006114966, WO2007063754, WO2008056746, WO2009003898, WO2009021126, WO2009063833, WO2009066778, WO2009066779, WO2009086028, WO2010056066, WO2010107244, WO2011081423, WO2011081431, WO2011086863, WO2012128298, WO2012133644, WO2012133649, WO2013024872, WO2013035275, WO2013081315, WO2013191404, WO2014142472,

Emitter:

An emitter example is not particularly limited, and any compound may be used as long as the compound is typically used as an emitter material. Examples of suitable emitter materials include, but are not limited to, compounds which can produce emissions via phosphorescence, fluorescence, thermally activated delayed fluorescence, i.e., TADF (also referred to as E-type delayed fluorescence), triplet-triplet annihilation, or combinations of these processes.

Non-limiting examples of the emitter materials that may be used in an OLED in combination with materials disclosed herein are exemplified below together with references that disclose those materials: CN103694277, CN1696137, EB01238981, EP01239526, EP01961743, EP1239526, EP1244155, EP1642951, EP1647554, EP1841834, EP1841834B, EP2062907, EP2730583, JP2012074444, JP2013110263, JP4478555, KR1020090133652, KR20120032054, KR20130043460, TW201332980, U.S. Ser. No. 06/699,599, U.S. Ser. No. 06/916,554, US20010019782, US20020034656, US20030068526, US20030072964, US20030138657, US20050123788, US20050244673, US2005123791, US2005260449, US20060008670, US20060065890, US20060127696, US20060134459, US20060134462, US20060202194, US20060251923, US20070034863, US20070087321, US20070103060, US20070111026, US20070190359, US20070231600, US2007034863, US2007104979, US2007104980, US2007138437, US2007224450, US2007278936, US20080020237, US20080233410, US20080261076, US20080297033, US200805851, US2008161567, US2008210930, US20090039776, US20090108737, US20090115322, US20090179555, US2009085476, US2009104472, US20100090591, US20100148663, US20100244004, US20100295032, US2010102716, US2010105902, US2010244004, US2010270916, US20110057559, US20110108822, US20110204333, US2011215710, US2011227049, US2011285275, US2012292601, US20130146848, US2013033172, US2013165653, US2013181190, US2013334521, US20140246656, US2014103305, U.S. Pat. No. 6,303,238, U.S. Pat. No. 6,413,656, U.S. Pat. No. 6,653,654, U.S. Pat. No. 6,670,645, U.S. Pat. No. 6,687,266, U.S. Pat. No. 6,835,469, U.S. Pat. No. 6,921,915, U.S. Pat. No. 7,279,704, U.S. Pat. No. 7,332,232, U.S. Pat. No. 7,378,162, U.S. Pat. No. 7,534,505, U.S. Pat. No. 7,675,228, U.S. Pat. No. 7,728,137, U.S. Pat. No. 7,740,957, U.S. Pat. No. 7,759,489, U.S. Pat. No. 7,951,947, U.S. Pat. No. 8,067,099, U.S. Pat. No. 8,592,586, U.S. Pat. No. 8,871,361, WO06081973, WO06121811, WO07018067, WO07108362, WO007115970, WO07115981, WO08035571, WO2002015645, WO2003040257, WO2005019373, WO2006056418, WO2008054584, WO2008078800, WO2008096609, WO2008101842, WO2009000673, WO2009050281, WO2009100991, WO2010028151, WO2010054731, WO2010086089, WO2010118029, WO2011044988, WO2011051404, WO2011107491, WO2012020327, WO2012163471, WO2013094620, WO2013107487, WO2013174471, WO2014007565, WO2014008982, WO2014023377, WO2014024131, WO2014031977, WO2014038456, WO2014112450,

HBL:

A hole blocking layer (HBL) may be used to reduce the number of holes and/or excitons that leave the emissive layer. The presence of such a blocking layer in a device may result in substantially higher efficiencies and/or longer lifetime as compared to a similar device lacking a blocking layer. Also, a blocking layer may be used to confine emission to a desired region of an OLED. In some embodiments, the HBL material has a lower HOMO (further from the vacuum level) and or higher triplet energy than the emitter closest to the HBL interface. In some embodiments, the HBL material has a lower HOMO (further from the vacuum level) and or higher triplet energy than one or more of the hosts closest to the HBL interface.

In one aspect, compound used in HBL contains the same molecule or the same functional groups used as host described above.

In another aspect, compound used in HBL contains at least one of the following groups in the molecule:

wherein k is an integer from 1 to 20; L¹⁰¹ is an another ligand, k′ is an integer from 1 to 3.

ETL:

Electron transport layer (ETL) may include a material capable of transporting electrons. Electron transport layer may be intrinsic (undoped), or doped. Doping may be used to enhance conductivity. Examples of the ETL material are not particularly limited, and any metal complexes or organic compounds may be used as long as they are typically used to transport electrons.

In one aspect, compound used in ETL contains at least one of the following groups in the molecule:

wherein R¹⁰¹ is selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof, when it is aryl or heteroaryl, it has the similar definition as Ar's mentioned above. Ar¹ to Ar³ has the similar definition as Ar's mentioned above. k is an integer from 1 to 20. X¹⁰¹ to X¹⁰⁸ is selected from C (including CH) or N.

In another aspect, the metal complexes used in ETL include, but are not limited to the following general formula:

wherein (O—N) or (N—N) is a bidentate ligand, having metal coordinated to atoms O, N or N, N; L¹⁰¹ is another ligand; k′ is an integer value from 1 to the maximum number of ligands that may be attached to the metal.

Non-limiting examples of the ETL materials that may be used in an OLED in combination with materials disclosed herein are exemplified below together with references that disclose those materials: CN103508940, EP01602648, EP01734038, EP01956007, JP2004-022334, JP2005149918, JP2005-268199, KR0117693, KR20130108183, US20040036077, US20070104977, US2007018155, US20090101870, US20090115316, US20090140637, US20090179554, US2009218940, US2010108990, US2011156017, US2011210320, US2012193612, US2012214993, US2014014925, US2014014927, US20140284580, U.S. Pat. No. 6,656,612, U.S. Pat. No. 8,415,031, WO2003060956, WO2007111263, WO2009148269, WO2010067894, WO2010072300, WO2011074770, WO2011105373, WO2013079217, WO2013145667, WO2013180376, WO2014104499, WO2014104535,

Charge Generation Layer (CGL)

In tandem or stacked OLEDs, the CGL plays an essential role in the performance, which is composed of an n-doped layer and a p-doped layer for injection of electrons and holes, respectively. Electrons and holes are supplied from the CGL and electrodes. The consumed electrons and holes in the CGL are refilled by the electrons and holes injected from the cathode and anode, respectively; then, the bipolar currents reach a steady state gradually. Typical CGL materials include n and p conductivity dopants used in the transport layers.

In any above-mentioned compounds used in each layer of the OLED device, the hydrogen atoms can be partially or fully deuterated. Thus, any specifically listed substituent, such as, without limitation, methyl, phenyl, pyridyl, etc. encompasses undeuterated, partially deuterated, and fully deuterated versions thereof. Similarly, classes of substituents such as, without limitation, alkyl, aryl, cycloalkyl, heteroaryl, etc. also encompass undeuterated, partially deuterated, and fully deuterated versions thereof.

EXPERIMENTAL Synthesis of Compound 1

Into a solution of benzofuro[3,2-b]pyridin-9-ol (18.5 g, 100 mol) in methanol is added LiOH hydrate (6.3 g, 150 mmol). The reaction mixture is stirred at room temperature for 24 hours. After quenching with water, the reaction mixture is extracted with ether, dried over MgSO₄. Upon evaporation of the solvent, the crude product is further purified by recrystallization to yield Compound 1 as a solid.

Synthesis of Compound 557

Into a degassed solution of 7,12-dihydropyrido[3,2-b:5,4-b′]diindol-4-ol (5.49 g, 20 mmol), Phenyl iodide (6.15 g, 30 mmol), K₂CO₃ (8.3 g, 60 mmol) in dimethylformamide are added CuI (0.2 g, 1 mmol) and 1,2-diaminocyclohexane (0.45 g, 4 mmol). The reaction mixture is refluxed under nitrogen for 24 h. After cooling to room temperature, the solid is removed by filtration and the filtrate is concentrated. The crude product is purified by column chromatography on silica gel with heptane/ethyl acetate as eluent to yield 7,12-diphenyl-7,12-dihydropyrido[3,2-b: 5,4-b′]diindol-4-ol as a solid.

Into a solution of 7,12-diphenyl-7,12-dihydropyrido[3,2-b:5,4-b′]diindol-4-ol (4.25 g, 10 mol) in methanol and dimethylformamide is added LiOH hydrate (0.63 g, 15 mmol). The reaction mixture is stirred at room temperature for 24 hours. After quenching with water, the reaction mixture is extracted with ether, dried over MgSO₄. Upon evaporation of the solvent, the crude product is further purified by recrystallization to yield Compound 557 as a solid.

It is understood that the various embodiments described herein are by way of example only, and are not intended to limit the scope of the invention. For example, many of the materials and structures described herein may be substituted with other materials and structures without deviating from the spirit of the invention. The present invention as claimed may therefore include variations from the particular examples and preferred embodiments described herein, as will be apparent to one of skill in the art. It is understood that various theories as to why the invention works are not intended to be limiting. 

We claim:
 1. A compound comprising a ligand L_(A) having the formula:

wherein X¹ is selected from the group consisting of O, S, Se, NR, CRR′, SiRR′, and

wherein L_(A) is coordinated to a metal M selected from the group consisting of Li, Be, Mg, Al, Ga, and Zn; wherein L_(A) is optionally linked with other ligands to comprise a tridentate to possible maximum dentate ligand; wherein M is optionally coordinated to other ligands; wherein when X¹ is selected from the group consisting of O, S, and Se; then M is Li; wherein when X¹ is selected from the group consisting of NR, CRR′, SiRR′; then at least one pair of adjacent Z¹ to Z³, or Z⁴ to Z⁶ are carbon atoms of which R¹ or R² attached thereto form a di-substitution having the following formula and are fused to ring A or B;

wherein the wave lines indicate bonds to ring A or B; wherein X² is selected from the group consisting of O, S, Se, NR, CRR′, and SiRR′; wherein Z¹ to Z¹⁴ are each independently selected from the group consisting of carbon and nitrogen; wherein R¹ to R⁴ each independently represent a mono to possible maximum number of substitution, or no substitution; wherein R¹ to R⁴, R, and R′ are each independently selected from the group consisting of hydrogen, deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; and wherein any two adjacent substituents are optionally joined to form a ring.
 2. The compound of claim 1, wherein X¹ is selected from the group consisting of O, S, and Se.
 3. The compound of claim 1, wherein X¹ is selected from the group consisting of NR, CRR′, and SiRR′.
 4. The compound of claim 1, wherein the ligand L_(A) is:


5. The compound of claim 1, wherein the ligand L_(A) is selected from the group consisting of:


6. The compound of claim 1, wherein Z¹ to Z¹⁴ are each a carbon atom.
 7. The compound of claim 1, wherein at least one of Z¹ to Z¹⁴ is nitrogen atom.
 8. The compound of claim 1, wherein one of Z¹ to Z¹⁴ is nitrogen atom, and the remaining Z¹ to Z¹⁴ are carbon atoms.
 9. The compound of claim 1, wherein each six-membered ring in the ligand L_(A) has no more than one nitrogen atom.
 10. The compound of claim 1, wherein the compound is selected from the group consisting of LiL_(A), Be(L_(A))₂, Mg(L_(A))₂, Al(L_(A))₃, Ga(L_(A))₃, and Zn(L_(A))₂.
 11. The compound of claim 1, wherein the compound is heteroleptic.
 12. The compound of claim 1, wherein the compound is selected from the group consisting of:

  Compound 1, wherein X¹ is O; Compound 2, wherein X¹ is S; Compound 3, wherein X¹ is Se;

  Compound 4, wherein X¹ is O; Compound 5, wherein X¹ is S; Compound 6, wherein X¹ is Se;

  Compound 7, wherein X¹ is O; Compound 8, wherein X¹ is S; Compound 9, wherein X¹ is Se;

  Compound 10, wherein X¹ is O; Compound 11, wherein X¹ is S; Compound 12, wherein X¹ is Se;

  Compound 13, wherein X¹ is O; Compound 14, wherein X¹ is S; Compound 15, wherein X¹ is Se;

  Compound 16, wherein X¹ is O; Compound 17, wherein X¹ is S; Compound 18, wherein X¹ is Se;

  Compound 19, wherein X¹ is O; Compound 20, wherein X¹ is S; Compound 21, wherein X¹ is Se;

  Compound 22, wherein X¹ is O; Compound 23, wherein X¹ is S; Compound 24, wherein X¹ is Se;

  Compound 25, wherein X¹ is O; Compound 26, wherein X¹ is S; Compound 27, wherein X¹ is Se;

  Compound 28, wherein X¹ is O; Compound 29, wherein X¹ is S; Compound 30, wherein X¹ is Se;

ID Structure n M Compound 31 Compound 32 Compound 33 Compound 34 Compound 35

1 2 3 3 2 Li Be Al Ga Zn Compound 36 Compound 37 Compound 38 Compound 39 Compound 40

1 2 3 3 2 Li Be Al Ga Zn Compound 41 Compound 42 Compound 43 Compound 44 Compound 45

1 2 3 3 2 Li Be Al Ga Zn Compound 46 Compound 47 Compound 48 Compound 49 Compound 50

1 2 3 3 2 Li Be Al Ga Zn Compound 51 Compound 52 Compound 53 Compound 54 Compound 55

1 2 3 3 2 Li Be Al Ga Zn Compound 56 Compound 57 Compound 58 Compound 59 Compound 60

1 2 3 3 2 Li Be Al Ga Zn Compound 61 Compound 62 Compound 63 Compound 64 Compound 65

1 2 3 3 2 Li Be Al Ga Zn Compound 66 Compound 67 Compound 68 Compound 69 Compound 70

1 2 3 3 2 Li Be Al Ga Zn Compound 71 Compound 72 Compound 73 Compound 74 Compound 75

1 2 3 3 2 Li Be Al Ga Zn Compound 76 Compound 77 Compound 78 Compound 79 Compound 80

1 2 3 3 2 Li Be Al Ga Zn Compound 81 Compound 82 Compound 83 Compound 84 Compound 85

1 2 3 3 2 Li Be Al Ga Zn ID Structure n M X¹ X² Compound 86 Compound 87 Compound 88 Compound 89 Compound 90 Compound 91 Compound 92 Compound 93 Compound 94 Compound 95 Compound 96 Compound 97 Compound 98 Compound 99 Compound 100 Compound 101

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Li Li Li Li Li Li Li Li Li Li Li Li Li Li Li Li O O O O O O S S S S S S Se Se Se Se O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 102 1 Li Se CMeMe Compound 103 1 Li Se SiMeMe Compound 104 1 Li NPh O Compound 105 1 Li NPh S Compound 106 1 Li NPh Se Compound 107 1 Li NPh NPh Compound 108 1 Li NPh CMeMe Compound 109 1 Li NPh SiMeMe Compound 110 1 Li CMeMe O Compound 111 1 Li CMeMe S Compound 112 1 Li CMeMe Se Compound 113 1 Li CMeMe NPh Compound 114 1 Li CMeMe CMeMe Compound 115 1 Li CMeMe SiMeMe Compound 116 1 Li SiMeMe O Compound 117 1 Li SiMeMe S Compound 118 1 Li SiMeMe Se Compound 119 1 Li SiMeMe NPh Compound 120 1 Li SiMeMe CMeMe Compound 121 1 Li SiMeMe SiMeMe Compound 122 Compound 123 Compound 124 Compound 125 Compound 126 Compound 127 Compound 128 Compound 129 Compound 130 Compound 131 Compound 132 Compound 133 Compound 134 Compound 135 Compound 136 Compound 137

2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Be Be Be Be Be Be Be Be Be Be Be Be Be Be Be Be NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 138 2 Be SiMeMe CMeMe Compound 139 2 Be SiMeMe SiMeMe Compound 140 Compound 141 Compound 142 Compound 143 Compound 144 Compound 145 Compound 146 Compound 147 Compound 148 Compound 149 Compound 150 Compound 151 Compound 152 Compound 153 Compound 154 Compound 155

3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 Al Al Al Al Al Al Al Al Al Al Al Al Al Al Al Al NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 156 3 Al SiMeMe CMeMe Compound 157 3 Al SiMeMe SiMeMe Compound 158 Compound 159 Compound 160 Compound 161 Compound 162 Compound 163 Compound 164 Compound 165 Compound 166 Compound 167 Compound 168 Compound 169 Compound 170 Compound 171 Compound 172 Compound 173

2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 174 2 Zn SiMeMe CMeMe Compound 175 2 Zn SiMeMe SiMeMe Compound 176 Compound 177 Compound 178 Compound 179 Compound 180 Compound 181 Compound 182 Compound 183 Compound 184 Compound 185 Compound 186 Compound 187 Compound 188 Compound 189 Compound 190 Compound 191

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Li Li Li Li Li Li Li Li Li Li Li Li Li Li Li Li O O O O O O S S S S S S Se Se Se Se O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 192 1 Li Se CMeMe Compound 193 1 Li Se SiMeMe Compound 194 1 Li NPh O Compound 195 1 Li NPh S Compound 196 1 Li NPh Se Compound 197 1 Li NPh NPh Compound 198 1 Li NPh CMeMe Compound 199 1 Li NPh SiMeMe Compound 200 1 Li CMeMe O Compound 201 1 Li CMeMe S Compound 202 1 Li CMeMe Se Compound 203 1 Li CMeMe NPh Compound 204 1 Li CMeMe CMeMe Compound 205 1 Li CMeMe SiMeMe Compound 206 1 Li SiMeMe O Compound 207 1 Li SiMeMe S Compound 208 1 Li SiMeMe Se Compound 209 1 Li SiMeMe NPh Compound 210 1 Li SiMeMe CMeMe Compound 211 1 Li SiMeMe SiMeMe Compound 212 Compound 213 Compound 214 Compound 215 Compound 216 Compound 217 Compound 218 Compound 219 Compound 220 Compound 221 Compound 222 Compound 223 Compound 224 Compound 225 Compound 226 Compound 227

2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Be Be Be Be Be Be Be Be Be Be Be Be Be Be Be Be NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 228 2 Be SiMeMe CMeMe Compound 229 2 Be SiMeMe SiMeMe Compound 230 Compound 231 Compound 232 Compound 233 Compound 234 Compound 235 Compound 236 Compound 237 Compound 238 Compound 239 Compound 240 Compound 241 Compound 242 Compound 243 Compound 244 Compound 245

3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 Al Al Al Al Al Al Al Al Al Al Al Al Al Al Al Al NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 246 3 Al SiMeMe CMeMe Compound 247 3 Al SiMeMe SiMeMe Compound 248 Compound 249 Compound 250 Compound 251 Compound 252 Compound 253 Compound 254 Compound 255 Compound 256 Compound 257 Compound 258 Compound 259 Compound 260 Compound 261 Compound 262 Compound 263

2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 264 2 Zn SiMeMe CMeMe Compound 265 2 Zn SiMeMe SiMeMe Compound 266 Compound 267 Compound 268 Compound 269 Compound 270 Compound 271 Compound 272 Compound 273 Compound 274 Compound 275 Compound 276 Compound 277 Compound 278 Compound 279 Compound 280

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Li Li Li Li Li Li Li Li Li Li Li Li Li Li Li O O O O O O S S S S S S Se Se Se O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se Compound 281 1 Li Se NPh Compound 282 1 Li Se CMeMe Compound 283 1 Li Se SiMeMe Compound 284 1 Li NPh O Compound 285 1 Li NPh S Compound 286 1 Li NPh Se Compound 287 1 Li NPh NPh Compound 288 1 Li NPh CMeMe Compound 289 1 Li NPh SiMeMe Compound 290 1 Li CMeMe O Compound 291 1 Li CMeMe S Compound 292 1 Li CMeMe Se Compound 293 1 Li CMeMe NPh Compound 294 1 Li CMeMe CMeMe Compound 295 1 Li CMeMe SiMeMe Compound 296 1 Li SiMeMe O Compound 297 1 Li SiMeMe S Compound 298 1 Li SiMeMe Se Compound 299 1 Li SiMeMe NPh Compound 300 1 Li SiMeMe CMeMe Compound 301 1 Li SiMeMe SiMeMe Compound 302 Compound 303 Compound 304 Compound 305 Compound 306 Compound 307 Compound 308 Compound 309 Compound 310 Compound 311 Compound 312 Compound 313 Compound 314 Compound 315 Compound 316

2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Be Be Be Be Be Be Be Be Be Be Be Be Be Be Be NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se Compound 317 2 Be SiMeMe NPh Compound 318 2 Be SiMeMe CMeMe Compound 319 2 Be SiMeMe SiMeMe Compound 320 Compound 321 Compound 322 Compound 323 Compound 324 Compound 325 Compound 326 Compound 327 Compound 328 Compound 329 Compound 330 Compound 331 Compound 332 Compound 333 Compound 334

3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 Al Al Al Al Al Al Al Al Al Al Al Al Al Al Al NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se Compound 335 3 Al SiMeMe NPh Compound 336 3 Al SiMeMe CMeMe Compound 337 3 Al SiMeMe SiMeMe Compound 338 Compound 339 Compound 340 Compound 341 Compound 342 Compound 343 Compound 344 Compound 345 Compound 346 Compound 347 Compound 348 Compound 349 Compound 350 Compound 351

2 2 2 2 2 2 2 2 2 2 2 2 2 2 Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Compound 352 2 Zn SiMeMe Se Compound 353 2 Zn SiMeMe NPh Compound 354 2 Zn SiMeMe CMeMe Compound 355 2 Zn SiMeMe SiMeMe Compound 356 Compound 357 Compound 358 Compound 359 Compound 360 Compound 361 Compound 362 Compound 363 Compound 364 Compound 365 Compound 366

1 1 1 1 1 1 1 1 1 1 1 Li Li Li Li Li Li Li Li Li Li Li O O O O O O S S S S S O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe Compound 367 1 Li S SiMeMe Compound 368 1 Li Se O Compound 369 1 Li Se S Compound 370 1 Li Se Se Compound 371 1 Li Se NPh Compound 372 1 Li Se CMeMe Compound 373 1 Li Se SiMeMe Compound 374 1 Li NPh O Compound 375 1 Li NPh S Compound 376 1 Li NPh Se Compound 377 1 Li NPh NPh Compound 378 1 Li NPh CMeMe Compound 379 1 Li NPh SiMeMe Compound 380 1 Li CMeMe O Compound 381 1 Li CMeMe S Compound 382 1 Li CMeMe Se Compound 383 1 Li CMeMe NPh Compound 384 1 Li CMeMe CMeMe Compound 385 1 Li CMeMe SiMeMe Compound 386 1 Li SiMeMe O Compound 387 1 Li SiMeMe S Compound 388 1 Li SiMeMe Se Compound 389 1 Li SiMeMe NPh Compound 390 1 Li SiMeMe CMeMe Compound 391 1 Li SiMeMe SiMeMe Compound 392 Compound 393 Compound 394 Compound 395 Compound 396 Compound 397 Compound 398 Compound 399 Compound 400 Compound 401 Compound 402 Compound 403

2 2 2 2 2 2 2 2 2 2 2 2 Be Be Be Be Be Be Be Be Be Be Be Be NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe Compound 404 2 Be SiMeMe O Compound 405 2 Be SiMeMe S Compound 406 2 Be SiMeMe Se Compound 407 2 Be SiMeMe NPh Compound 408 2 Be SiMeMe CMeMe Compound 409 2 Be SiMeMe SiMeMe Compound 410 Compound 411 Compound 412 Compound 413 Compound 414 Compound 415 Compound 416 Compound 417 Compound 418 Compound 419 Compound 420 Compound 421

3 3 3 3 3 3 3 3 3 3 3 3 Al Al Al Al Al Al Al Al Al Al Al A1 NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe Compound 422 3 Al SiMeMe O Compound 423 3 Al SiMeMe S Compound 424 3 Al SiMeMe Se Compound 425 3 Al SiMeMe NPh Compound 426 3 Al SiMeMe CMeMe Compound 427 3 Al SiMeMe SiMeMe Compound 428 Compound 429 Compound 430 Compound 431 Compound 432 Compound 433 Compound 434 Compound 435 Compound 436 Compound 437 Compound 438 Compound 439

2 2 2 2 2 2 2 2 2 2 2 2 Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe Compound 440 2 Zn SiMeMe O Compound 441 2 Zn SiMeMe S Compound 442 2 Zn SiMeMe Se Compound 443 2 Zn SiMeMe NPh Compound 444 2 Zn SiMeMe CMeMe Compound 445 2 Zn SiMeMe SiMeMe Compound 446 Compound 447 Compound 448 Compound 449 Compound 450 Compound 451 Compound 452 Compound 453 Compound 454 Compound 455 Compound 456 Compound 457 Compound 458 Compound 459 Compound 460 Compound 461

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Li Li Li Li Li Li Li Li Li Li Li Li Li Li Li Li O O O O O O S S S S S S Se Se Se Se O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 462 1 Li Se CMeMe Compound 463 1 Li Se SiMeMe Compound 464 1 Li NPh O Compound 465 1 Li NPh S Compound 466 1 Li NPh Se Compound 467 1 Li NPh NPh Compound 468 1 Li NPh CMeMe Compound 469 1 Li NPh SiMeMe Compound 470 1 Li CMeMe O Compound 471 1 Li CMeMe S Compound 472 1 Li CMeMe Se Compound 473 1 Li CMeMe NPh Compound 474 1 Li CMeMe CMeMe Compound 475 1 Li CMeMe SiMeMe Compound 476 1 Li SiMeMe O Compound 477 1 Li SiMeMe S Compound 478 1 Li SiMeMe Se Compound 479 1 Li SiMeMe NPh Compound 480 1 Li SiMeMe CMeMe Compound 481 1 Li SiMeMe SiMeMe Compound 482 Compound 483 Compound 484 Compound 485 Compound 486 Compound 487 Compound 488 Compound 489 Compound 490 Compound 491 Compound 492 Compound 493 Compound 494 Compound 495 Compound 496 Compound 497 Compound 498

2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Be Be Be Be Be Be Be Be Be Be Be Be Be Be Be Be Be NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe Compound 499 2 Be SiMeMe SiMeMe Compound 500 Compound 501 Compound 502 Compound 503 Compound 504 Compound 505 Compound 506 Compound 507 Compound 508 Compound 509 Compound 510 Compound 511 Compound 512 Compound 513 Compound 514 Compound 515

3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 Al Al Al Al Al Al Al Al Al Al Al Al Al Al Al Al NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 516 3 Al SiMeMe CMeMe Compound 517 3 Al SiMeMe SiMeMe Compound 518 Compound 519 Compound 520 Compound 521 Compound 522 Compound 523 Compound 524 Compound 525 Compound 526 Compound 527 Compound 528 Compound 529 Compound 530 Compound 531 Compound 532 Compound 533

2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 534 2 Zn SiMeMe CMeMe Compound 535 2 Zn SiMeMe SiMeMe Compound 536 Compound 537 Compound 538 Compound 539 Compound 540 Compound 541 Compound 542 Compound 543 Compound 544 Compound 545 Compound 546 Compound 547 Compound 548 Compound 549 Compound 550

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Li Li Li Li Li Li Li Li Li Li Li Li Li Li Li O O O O O O S S S S S S Se Se Se O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se Compound 551 1 Li Se NPh Compound 552 1 Li Se CMeMe Compound 553 1 Li Se SiMeMe Compound 554 1 Li NPh O Compound 555 1 Li NPh S Compound 556 1 Li NPh Se Compound 557 1 Li NPh NPh Compound 558 1 Li NPh CMeMe Compound 559 1 Li NPh SiMeMe Compound 560 1 Li CMeMe O Compound 561 1 Li CMeMe S Compound 562 1 Li CMeMe Se Compound 563 1 Li CMeMe NPh Compound 564 1 Li CMeMe CMeMe Compound 565 1 Li CMeMe SiMeMe Compound 566 1 Li SiMeMe O Compound 567 1 Li SiMeMe S Compound 568 1 Li SiMeMe Se Compound 569 1 Li SiMeMe NPh Compound 570 1 Li SiMeMe CMeMe Compound 571 1 Li SiMeMe SiMeMe Compound 572 Compound 573 Compound 574 Compound 575 Compound 576 Compound 577 Compound 578 Compound 579 Compound 580 Compound 581 Compound 582 Compound 583 Compound 584 Compound 585 Compound 586

2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Be Be Be Be Be Be Be Be Be Be Be Be Be Be Be NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se Compound 587 2 Be SiMeMe NPh Compound 588 2 Be SiMeMe CMeMe Compound 589 2 Be SiMeMe SiMeMe Compound 590 Compound 591 Compound 592 Compound 593 Compound 594 Compound 595 Compound 596 Compound 597 Compound 598 Compound 599 Compound 600 Compound 601 Compound 602 Compound 603 Compound 604

3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 Al Al Al Al Al Al Al Al Al Al Al Al Al Al Al NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe SiMeMe Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe Compound 605 3 Al SiMeMe SiMeMe Compound 606 Compound 607 Compound 608 Compound 609 Compound 610 Compound 611 Compound 612 Compound 613 Compound 614 Compound 615 Compound 616 Compound 617 Compound 618 Compound 619 Compound 620

2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se Compound 621 2 Zn SiMeMe NPh Compound 622 2 Zn SiMeMe CMeMe Compound 623 2 Zn SiMeMe SiMeMe Compound 624 Compound 625 Compound 626 Compound 627 Compound 628 Compound 629 Compound 630 Compound 631 Compound 632 Compound 633 Compound 634 Compound 635 Compound 636

1 1 1 1 1 1 1 1 1 1 1 1 1 Li Li Li Li Li Li Li Li Li Li Li Li Li O O O O O O S S S S S S Se O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O Compound 637 1 Li Se S Compound 638 1 Li Se Se Compound 639 1 Li Se NPh Compound 640 1 Li Se CMeMe Compound 641 1 Li Se SiMeMe Compound 642 1 Li NPh O Compound 643 1 Li NPh S Compound 644 1 Li NPh Se Compound 645 1 Li NPh NPh Compound 646 1 Li NPh CMeMe Compound 647 1 Li NPh SiMeMe Compound 648 1 Li CMeMe O Compound 649 1 Li CMeMe S Compound 650 1 Li CMeMe Se Compound 651 1 Li CMeMe NPh Compound 652 1 Li CMeMe CMeMe Compound 653 1 Li CMeMe SiMeMe Compound 654 1 Li SiMeMe O Compound 655 1 Li SiMeMe S Compound 656 1 Li SiMeMe Se Compound 657 1 Li SiMeMe NPh Compound 658 1 Li SiMeMe CMeMe Compound 659 1 Li SiMeMe SiMeMe Compound 660 Compound 661 Compound 662 Compound 663 Compound 664 Compound 665 Compound 666 Compound 667 Compound 668 Compound 669 Compound 670 Compound 671 Compound 672

2 2 2 2 2 2 2 2 2 2 2 2 2 Be Be Be Be Be Be Be Be Be Be Be Be Be NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O Compound 673 2 Be SiMeMe S Compound 674 2 Be SiMeMe Se Compound 675 2 Be SiMeMe NPh Compound 676 2 Be SiMeMe CMeMe Compound 677 2 Be SiMeMe SiMeMe Compound 678 Compound 679 Compound 680 Compound 681 Compound 682 Compound 683 Compound 684 Compound 685 Compound 686 Compound 687 Compound 688 Compound 689 Compound 690

3 3 3 3 3 3 3 3 3 3 3 3 3 Al Al Al Al Al Al Al Al Al Al Al Al Al NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O Compound 691 3 Al SiMeMe S Compound 692 3 Al SiMeMe Se Compound 693 3 Al SiMeMe NPh Compound 694 3 Al SiMeMe CMeMe Compound 695 3 Al SiMeMe SiMeMe Compound 696 Compound 697 Compound 698 Compound 699 Compound 700 Compound 701 Compound 702 Compound 703 Compound 704 Compound 705 Compound 706 Compound 707 Compound 708

2 2 2 2 2 2 2 2 2 2 2 2 2 Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O Compound 709 2 Zn SiMeMe S Compound 710 2 Zn SiMeMe Se Compound 711 2 Zn SiMeMe NPh Compound 712 2 Zn SiMeMe CMeMe Compound 713 2 Zn SiMeMe SiMeMe Compound 714 Compound 715 Compound 716 Compound 717 Compound 718 Compound 719 Compound 720 Compound 721 Compound 722 Compound 723 Compound 724 Compound 725 Compound 726 Compound 727 Compound 728 Compound 729

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Li Li Li Li Li Li Li Li Li Li Li Li Li Li Li Li O O O O O O S S S S S S Se Se Se Se O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 730 1 Li Se CMeMe Compound 731 1 Li Se SiMeMe Compound 732 1 Li NPh O Compound 733 1 Li NPh S Compound 734 1 Li NPh Se Compound 735 1 Li NPh NPh Compound 736 1 Li NPh CMeMe Compound 737 1 Li NPh SiMeMe Compound 738 1 Li CMeMe O Compound 739 1 Li CMeMe S Compound 740 1 Li CMeMe Se Compound 741 1 Li CMeMe NPh Compound 742 1 Li CMeMe CMeMe Compound 743 1 Li CMeMe SiMeMe Compound 744 1 Li SiMeMe O Compound 745 1 Li SiMeMe S Compound 746 1 Li SiMeMe Se Compound 747 1 Li SiMeMe NPh Compound 748 1 Li SiMeMe CMeMe Compound 749 1 Li SiMeMe SiMeMe Compound 750 Compound 751 Compound 752 Compound 753 Compound 754 Compound 755 Compound 756 Compound 757 Compound 758 Compound 759 Compound 760 Compound 761 Compound 762 Compound 763 Compound 764 Compound 765

2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Be Be Be Be Be Be Be Be Be Be Be Be Be Be Be Be NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 766 2 Be SiMeMe CMeMe Compound 767 2 Be SiMeMe SiMeMe Compound 768 Compound 769 Compound 770 Compound 771 Compound 772 Compound 773 Compound 774 Compound 775 Compound 776 Compound 777 Compound 778 Compound 779 Compound 780 Compound 781 Compound 782 Compound 783

3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 Al Al Al Al Al Al Al Al Al Al Al Al Al Al Al Al NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 784 3 Al SiMeMe CMeMe Compound 785 3 Al SiMeMe SiMeMe Compound 786 Compound 787 Compound 788 Compound 789 Compound 790 Compound 791 Compound 792 Compound 793 Compound 794 Compound 795 Compound 796 Compound 797 Compound 798 Compound 799 Compound 800 Compound 801

2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn Zn NPh NPh NPh NPh NPh NPh CMeMe CMeMe CMeMe CMeMe CMeMe CMeMe SiMeMe SiMeMe SiMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh CMeMe SiMeMe O S Se NPh Compound 802 2 Zn SiMeMe CMeMe Compound 803 2 Zn SiMeMe SiMeMe


13. An organic light emitting device (OLED) comprising: an anode; a cathode; and a first organic layer, disposed between the anode and the cathode, comprising a compound comprising a ligand L_(A) having the formula:

wherein X¹ is selected from the group consisting of O, S, Se, NR, CRR′, SiRR′, and

wherein L_(A) is coordinated to a metal M selected from the group consisting of Li, Be, Mg, Al, Ga, and Zn; wherein L_(A) is optionally linked with other ligands to comprise a tridentate to possible maximum dentate ligand; wherein M is optionally coordinated to other ligands; wherein when X¹ is selected from the group consisting of O, S, and Se; then M is Li; wherein when X¹ is selected from the group consisting of NR, CRR′, SiRR′; then at least a pair of adjacent Z¹ to Z³, or Z⁴ to Z⁶ are carbon atoms of which R¹ or R² attached thereto form a di-substitution having the following formula and fuse to ring A or B;

wherein the wave lines indicate bonds to ring A or B; wherein X² is selected from the group consisting of O, S, Se, NR, CRR′, and SiRR′; wherein Z¹ to Z¹⁴ are each independently selected from the group consisting of carbon and nitrogen; wherein R¹ to R⁴ each independently represent a mono to possible maximum number of substitution, or no substitution; wherein R¹ to R⁴, R, and R′ are each independently selected from the group consisting of hydrogen, deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; and wherein any two adjacent substituents are optionally joined to form a ring.
 14. The OLED of claim 13, wherein the first organic layer is an electron injecting layer.
 15. The OLED of claim 13, wherein the OLED comprises a second organic layer, wherein the second organic layer is an emitting layer comprising a phosphorescent emissive dopant; wherein the emissive dopant is a transition metal complex having at least one ligand or part of the ligand if the ligand is more than bidentate selected from the group consisting of:

wherein each X¹ to X¹³ are independently selected from the group consisting of carbon and nitrogen; wherein X is selected from the group consisting of BR′, NR′, PR′, O, S, Se, C═O, S═O, SO₂, CR′R″, SiR′R″, and GeR′R″; wherein R′ and R″ are optionally fused or joined to form a ring; wherein each R_(a), R_(b), R_(c), and R_(d) may represent from mono substitution to the possible maximum number of substitution, or no substitution; wherein R′, R″, R_(a), R_(b), R_(c), and R_(d) are each independently selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; and wherein any two adjacent substituents of R_(a), R_(b), R_(c), and R_(d) are optionally fused or joined to form a ring or form a multidentate ligand.
 16. The OLED of claim 13, wherein the OLED is incorporated into a device selected from the group consisting of a consumer product, an electronic component module, and a lighting panel.
 17. A formulation comprising a compound according to claim
 1. 